Wiper device and method for adjusting the bearing force of a wiper arm

ABSTRACT

Wiper apparatus and method, in particular for a motor vehicle, having a wiper arm ( 10 ) that is connectable to a wiper blade ( 13 ) on its one end ( 12 ) and, in the region of its other end ( 14 ), is connected to a tensioning element ( 22 ) that presses the one end ( 12 ) of the wiper arm ( 13 ) in the direction of a wiped surface ( 20 ) using a force F, whereby a calibrating element, in particular an eccentric bolt ( 30 ), is provided to adjust the force F.

BACKGROUND OF THE INVENTION

The invention concerns a wiper apparatus and a method for calibratingthe contact force of a wiper arm.

Numerous wiper apparatuses for motor vehicles are already known in whicha wiper blade attached to a wiper arm is pressed against the windshieldof the motor vehicle with the aid of an extension spring to produce awiper arm contact force. For this purpose, the wiper arm is attached inpivoting fashion to a rotary head using a hinge bolt, which rotary headis connected to the wiper shaft in torsion-proof fashion and makes anoscillating motion, for example. On the side facing the windshield, oneend of the extension spring is thereby hooked in a bolt with one end atthe wiper arm and with its other end on the rotary head. In suchsystems, the contact force can be varied or adjusted only by replacingthe spring or one of the clamps holding the spring with another springor another clamp.

SUMMARY OF THE INVENTION

The wiper apparatus has the advantage that the wiper arm contact forcecan be adjusted individually for any single wiper apparatus using aneccentric bolt as the calibrating element.

A relatively great deviation of contact forces between the individualwiper apparatuses in a series occurs as a result of tolerances of thespring rate and positional tolerances of the components that determinethe arrangement of the spring and the spring preload itself. As a resultof this, the mean contact force of all wiper apparatuses in a seriesmust be specified such that a good wiping quality is also given when thecontact force of the particular wiper apparatus moves on the margin ofthe tolerance range of the series. This is limited, on the one hand, bythe wiper motor, because, due to its design, the contact force is usedin the calculation linearly and, at maximum contact force—i.e., maximumfriction force of the wiper blade element—the wiper motor must alwaysremain capable of operating the wiper apparatus. On the other hand, thetolerance range is limited by the high-speed behavior. An acceptablewiping result must be achieved with a minimal contact force of the wiperarm and, therefore, the wiper blade, even at high speeds.

Using the calibrating element, a predetermined wiper arm contact forcecan be adjusted in very simple fashion, without using additionalcomponents or replacing them in entirety.

If one end of the wiper arm is connected to a rotary head in pivotingfashion, and the tensioning element between the wiper arm and rotaryhead is loaded, the contact force can be adjusted exactly, e.g., on aseparate test stand, and the combination of rotary head, tensioningelement and wiper arm can then installed on the wiper apparatus.

If the tensioning element on the rotary head is hooked around theeccentric bolt, it can be installed quickly, and it transfers thecalibrating motion evenly.

In addition, if the tensioning element comprises at least one extensionspring that is hooked around the eccentric bolt using a hook, thencommercially-available, cost-effective extension springs can be used.

If the calibrating element comprises an external straight knurling forfixation purposes, then, in advantageous fashion, it cannot be twistedduring operation as a result of the torque acting on the eccentric bolt,which would eliminate the calibration.

It is particularly advantageous if the calibrating element comprises asquare socket or external square, a slit, or a cross recession for thecalibration procedure. This is therefore easy to carry out using acommercially-available tool.

It is particularly advantageous, thereby, if the eccentric bolt issecured after turning. This can be accomplished, for example, by meansof riveting, stamping, pressing or welding.

It is furthermore advantageous if the eccentric bolt comprises threecylindrical sections, whereby the two outer sections along itslongitudinal extension comprise a coaxial centerline, and the centersection comprises a centerline—axis-parallel, in particular—that differsfrom the coaxial centerline. In this fashion, it is not only possible tochange the preload of the tensioning element, it is also possible tochange the preload of the torque acting on the wiper arm, because thedistance between the spring force that acts on the axis-parallelcenterline and the hinging bolt is changed when the eccentric bolt isturned.

If the two outer sections have different diameters, the eccentric boltis easier to insert during installation and it is secured againstfalling out, for example. It is also advantageous hereby, of course, ifthe bolt comprises a chamfer on at least one side.

If the eccentric bolt can be inserted in the bore of the rotary head andcomprises a partial straight knurling along one of its two outersections, it is advantageous if the center section of the eccentric boltis designed so—in particular, is at least so wide—that the tensioningelement can be hooked into the eccentric bolt without the straightknurling and bore being in contact. In this fashion, the eccentric boltcan be inserted into the bore during assembly, the tensioning elementcan be calibrated, and then the eccentric bolt can be prevented fromturning by driving it home, because this creates a positive andnon-positive connection between the bore and the eccentric bolt onlyafter calibration is completed.

The advantage of the method —based on the invention—according to claim 1is that a positive connection is achieved between eccentric bolt androtary head without having to sacrifice the accuracy of calibration,because the eccentric bolt can be driven home in any angular position.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is shown in the drawings anddescribed in greater detail in the subsequent description.

FIG. 1a shows a wiper arm with wiper blade and a rotary head of a wiperapparatus according to the invention,

FIG. 1b shows a schematic detailed view of the tensioning element hookedin place,

FIG. 2 shows a perspective drawing of an eccentric bolt, and

FIG. 3a shows schematic sectional view of an eccentric bolt withstraight knurling during installation, and

FIG. 3b shows an eccentric bolt as in FIG. 3a, after locking.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1a shows a wiper arm 10 of a wiper apparatus according to theinvention. It comprises two ends, with a wiper blade 13 attached to oneend 12. At the other end 14, the wiper arm 10 is hinge-mounted to arotary head 16 in pivoting fashion using a hinge bolt 15. On its endopposite to the wiper arm 10, the rotary head 16 comprises a containerliner 18 for attachment to a drive shaft (not shown) of the wiperapparatus. The wiper blade 13, which contacts a wiped surface 20, ishinge-mounted on one end 12 of the wiper arm 10. If the wiper apparatusis installed in a motor vehicle, the wiped surface is the windshield orrear window of the vehicle.

A tensioning element 22 is attached to the other end 14 of the wiper arm10 on the side of the wiper arm 10 facing the wiped surface 20. Itcomprises an extension spring 24 and a hook 26, each of which is hookedin place under pretension on the side of the wiper arm 10 and the rotaryhead 16 facing the wiped surface 20. By loading the tensioning element22, the wiper arm 10 is pressed with the force F in the direction of thewiped surface 20 with its one end 12 around its hinge bolt 15.

The other end of the wiper arm 10 is shown in detail in FIG. 1b with thetensioning element 22. The extension spring 24 of the tensioning element22 is hooked around a transverse bolt 28 between the two flanks of theU-shaped cross-section of the wiper arm 10. The transverse bolt 28extends through the U-shaped cross-section of the wiper arm 10 at adistance A from the hinge bolt 15. On its other side, the extensionspring 24 hooks into the hook 26 which, in turn, is hooked around aneccentric bolt 30 as the calibrating element. As a result, a torque actson the wiper arm 10 around the hinge bolt. The eccentric bolt 30 therebysits completely inside a bore 42 of the rotary head 16. The load on theextension spring 24 can be changed in this fashion by turning theeccentric bolt 30. This changes the contact force F with which the oneend 12 of the wiper arm presses the wiper blade 13 against the wipedsurface 20.

The eccentric bolt 30 is shown in detail in FIG. 2. It basicallycomprises three cylindrical sections, whereby the two outer sections 32extending along its longitudinal extension comprise a coaxial centerline34. The centerline of the center section 36 is different from thecoaxial centerline 34, in particular, axis-parallel to the coaxialcenterline 34.

The radius of the center section 36 is always smaller or equal to thedifference between the radius of the outer sections 32 and the distancebetween the coaxial centerline 34 and the axis-parallel centerline 46.In other words, the center section 36 in cross-section is always withinthe circle defined by the outer sections 32 in cross-section. Otherwise,it would not be possible to insert the eccentric bolt 30 into the bore42.

On at least one of its end surfaces 38, the eccentric bolt 30 comprisesa slit 40 that allows the eccentric bolt 30 to be turned within the bore42 of the rotary head 16. It is also possible, of course, to locate across recession or a square socket or external square on the end surface38 so that calibration can be carried out using commercially-availabletools. If the eccentric bolt 30 is inserted in the bore 42 of the rotaryhead 16, the contact force F or the load of the tensioning element 22can be adjusted by turning the eccentric bolt 30, then the eccentricbolt can be secured against rotation by means of riveting, stamping,pressing or welding.

To prevent the eccentric bolt 30 from falling through duringinstallation, the two outer sections 32 can also have different radii.

A sectional view through a rotary head 16 in the region of the eccentricbolt 30 is shown in FIG. 3. The eccentric bolt thereby comprises astraight knurling 44, as a fastening element, on one of its outersections 32 on the side opposite to the center section 36. The centersection 36 is dimensioned with regard for its longitudinal extension sothat the hook 26 of the tensioning element 22 can be hooked around thecenter section 36 without the straight knurling 44 being in contact withthe bore 42. In this fashion, the contact force F can be calibrated,and, at the end of the calibration procedure, the eccentric bolt 30 canbe pressed into the bore and thereby locked, so that a positiveconnection between the bore 42 and straight knurling 44 prevents theeccentric bolt 30 from turning. This is illustrated in FIG. 3b.

The method—based on the invention—according to claim 11 can be carriedout using an eccentric bolt 30 shown in FIG. 3. The eccentric bolt 30thereby comprises a straight knurling 44 along part of its longitudinalextension, as the fastening element.

In the first step, the eccentric bolt 30 is inserted in the bore 42, butonly so far that the straight knurling 44 is not yet lowered into thebore 42. The center section of the eccentric bolt 30 is so wide thatthis partial insertion alone is sufficient to hook the hook 26 of thetensioning element 22 around the eccentric bolt.

In a second step, the contact force F is adjusted by turning theeccentric bolt 30. In a third step, the eccentric bolt 30 is pressedinto the bore 42 so that the straight knurling 44 brings about apositive or non-positive connection with the bore 42.

Of course, a polygon, a single cam, or the like can also be used insteadof the straight knurling 44 as the fastening element.

In a variation of the invention, a bolt can be used instead of theeccentric bolt 30 that comprises a penetrating screw element in thecenter region along its longitudinal extension. If this is in contactwith the hook 26 by way of its side opposite to the head, the head ofthe screw element can be turned, thereby increasing the spring preload,to perform calibration.

What is claimed is:
 1. Wiper apparatus, in particular, for a motorvehicle, having a wiper arm (10) that is connectable to a wiper blade(13) on its one end (12) and, at a distance (A) from its other end (14),is connected to a tensioning element (22) that presses the one end (12)of the wiper arm (10) in the direction of a wiped surface (20) using aforce F, wherein a calibrating element, is provided to adjust the ForceF, wherein the tensioning element comprises at least one extensionspring and wherein the calibrating element is an eccentric bolt. 2.Wiper apparatus according to claim 1, wherein the wiper arm (10) isconnected at its other end (14) in pivoting fashion to a swivel head(16), and the tensioning element (22) is loaded between the wiper arm(10) and swivel head (16).
 3. Wiper apparatus according to claim 1,wherein the tensioning element (22) is hooked around the calibratingelement (30) at the swivel head (16).
 4. Wiper apparatus according toclaim 1, wherein the tensioning element (22) is hooked around thecalibrating element (30) by means of a hook (26).
 5. Wiper apparatusaccording to claim 1, wherein the calibrating element (30) comprises astraight knurling (44) for the purpose of fixation.
 6. Wiper apparatusaccording to claim 1, wherein the calibrating element (30) comprises asquare socket or external square, a slit (40), or a cross recession onits end surface for the purpose of calibration.
 7. Wiper apparatusaccording to claim 1, wherein the calibrating element (30) is securedagainst rotation, especially by means of riveting, stamping, pressing orwelding.
 8. Wiper apparatus according to claim 1, wherein thecalibrating element comprises three cylindrical sections (32, 26),whereby two outer sections (32) along the longitudinal extensioncomprise a coaxial centerline (34), and a center section (36) comprisesan axis-parallel centerline (46) that differs from the coaxialcenterline (34).
 9. Wiper apparatus according to claim 8, wherein thetwo outer sections (32) have different diameters.
 10. Wiper apparatusaccording to claim 8, wherein the eccentric bolt (30) is insertable intoa bore (42) of swivel head, comprises a partial straight knurling (44),particularly in the axial direction, along one of the two outer sections(32) for locking purposes, and its center section (36) is designed sothat the tensioning element (22) is able to be calibrated without thestraight knurling (44) and bore (42) being in contact.
 11. Method foradjusting a contact force of a wiper arm (10) of a wiper apparatus, saidarm including a tensioning element therein coupled to an eccentric bolt,said method comprising at least the following steps: partial insertionof the eccentric bolt (30) comprising—at least partially—a fasteningelement, in particular a straight knurling (44), along its longitudinalextension, into a bore (42) in the wiper arm leaving essential sectionsof said fastening element outside said bore, adjustment of the contactforce at least by means of turning said bolt, pressing of the eccentricbolt (30) inward at least so far that said essential sections of thefastening element (44) are located within the bore (42).